KR20010089180A - Hydrocracking method and catalyst - Google Patents

Abstract

In the hydrocracking method of the present invention, as a pretreatment, an organic nitrogen compound having a boiling point lower than 50% of the effluent oil is contacted with a catalyst for hydrocracking. Hydrocracking is carried out by bringing a hydrocracking catalyst into contact with crude oil and hydrogen to obtain hydrocarbons having a lower boiling point than crude oil. The pretreatment may also be carried out by contacting a petroleum fraction containing an organic nitrogen compound with a 95% distillation temperature lower than the 50% distillation temperature of the crude oil in contact with a catalyst for hydrocracking. As a result, the initial deterioration rate of the hydrocracking catalyst can be alleviated, the yield of the intermediate fraction can be improved, and further, the activity after the end of the initial deterioration can be improved.

Description

Hydrocracking Method and Hydrocracking Catalyst {HYDROCRACKING METHOD AND CATALYST}

Recently, attention has been focused on hydrocracking as a method of obtaining light oil by cracking heavy oil. The reason is that not only gasoline but also intermediate distillation products such as kerosene and gas oil can be obtained by hydrocracking, and their yield can be changed according to the operating conditions. This is because it is of high quality suitable for the environment.

As one of the hydrocracking methods, two-stage hydrocracking is known. The two-stage hydrocracking process is carried out using a two-stage hydrocracking system as shown, for example, in FIG. In this method, hydrogen and crude oil are fed to a first-stage reactor (or hydrorefining area) 41 filled with a hydrocracking catalyst, where the crude oil is hydrocracked. The hydrocracking is carried out simultaneously with the hydrocracking of the crude oil to remove in advance the nitrogenous compound which is a poison of the hydrocracking catalyst charged in the second-stage reactor 45. . The outlet oil discharged from the first stage reactor 41 is transferred to the distillation column 43, where light fractions are discharged, and a portion of the remaining heavy oil is transferred to the second stage reactor 45. Recycled. The nitrogen concentration in the heavy oil recycled to the hydrocracking catalyst of the second stage reactor 45 is less than 100 ppm. The product oil hydrocracked in the second stage reactor 45 is transferred to the distillation column 43 together with the outlet oil of the first stage reactor 41.

By the way, the hydrocracking catalyst used in the second stage reactor 45 of the two-stage hydrocracking process is usually vaporized by introducing a sulfiding agent into the hydrogen stream before starting the hydrocracking operation. Preliminary sulfide). Therefore, the catalyst (acid site of) charged in the second stage reactor 45 is not poisoned by nitrogen during the preliminary sulfidation.

However, although the catalyst charged in the second stage 45 is initially highly active, once the hydrocracking operation is started, nitrogen poisoning is caused by the nitrogen compound in the recirculating oil and rapidly deteriorates. In addition, when a bulky nitrogen compound, such as a polycyclic aromatic in a recirculating oil or a compound having a side chain attached to a carbazole, is adsorbed at the acid site of the catalyst, coke deactivation occurs, and as a result, an active site around the acid site where the nitrogen compound is adsorbed The active site is also poisoned, resulting in a decrease in activity after the initial degradation.

Therefore, in order to prevent such a hydrocracking catalyst from being deteriorated, a technique of pretreating the catalyst with ammonia before or during the hydrocracking operation is known. These techniques are disclosed in US Pat. And 5,366,615. Moreover, the technique of treating a catalyst by adding nitrogen compounds, such as a basic nitrogen compound, and ammonia to a hydrogenation refinery recycle oil during hydrocracking operation is also known. Such techniques are disclosed in US Pat. Nos. 3,213,013, 3,404,085, 3,505,208, and 3,816,296.

However, according to the studies of the present inventors, it is difficult to sustain the deterioration preventing effect of the catalyst for a long enough time by the method of treating the catalyst with ammonia before or after the hydrocracking operation. Further, the treatment using a low boiling point nitrogen compound such as butylamine disclosed in U.S. Patent No. 3,213,013 immediately proceeds with the hydrogenation tablet, so that the deterioration preventing effect of the catalyst does not last long enough. Furthermore, the conventional additives require a relatively large amount of nitrogen compound to be added in an amount of 5 to 200 ppm (nitrogen concentration).

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrocracking method for decomposing crude oil such as petroleum, and a catalyst for hydrocracking used therein. It is about.

1 is a process flow diagram of a hydrocracking system capable of implementing the hydrocracking method of the present invention.

2 is a process flow diagram of another hydrocracking system capable of implementing the hydrocracking process of the present invention.

3 is a process flow diagram of a hydrocracking system capable of implementing the hydrocracking method of the present invention with a recycling system.

4 is a process flow diagram of a two stage hydrocracking system capable of implementing the hydrocracking method of the present invention.

5 is a process flow diagram of a series flow hydrocracking system capable of implementing the hydrocracking method of the present invention.

The present invention has been made to solve the problems of the prior art, the object of which is to reduce the initial degradation rate of the hydrocracking catalyst, to improve the middle fraction yield, and also to improve the activity after the initial degradation end hydrocracking method And a hydrocracking catalyst used for the same.

According to the first aspect of the present invention, in the hydrocracking method of hydrocarbon oil,

Contacting a catalyst for hydrocracking with an organic nitrogen compound in advance; And

Contacting hydrogen with crude oil consisting essentially of hydrocarbon oil to a hydrocracking catalyst contacted with the organic nitrogen compound to obtain hydrocarbon oil having a lower boiling point than crude oil;

Including,

There is provided a hydrocracking method wherein the organic nitrogen compound is an organic nitrogen compound having a boiling point lower than 50% distillation temperature of the crude oil and higher than 200 ° C.

The inventors of the present invention have found that the acid point of the hydrocracking catalyst may be appropriately absorbed in order to (i) alleviate the initial degradation rate of the hydrocracking catalyst, (ii) improve the middle fraction yield, and (iii) improve the activity after the initial degradation. It has been found effective to coat (poison) with organic nitrogen compounds having the appropriate molecular size. The organic nitrogen compound used in the present invention is an organic nitrogen compound having a boiling point lower than the 50% distillation temperature of the raw material oil and having a boiling point higher than 200 ° C. The lower boiling point than the 50% effluent temperature of the crude oil is due to the exclusion of organic nitrogen compounds with too large a molecular size. Also more preferred are organic nitrogen compounds having a boiling point lower than (50% distillation temperature (° C.)) × 0.9. The organic nitrogen compound must have a boiling point higher than 200 ° C for the following reasons. That is, it is thought that the organic nitrogen compound which has a boiling point of 200 degrees C or less cannot fully cover (adsorb | suck) the acid point of the catalyst easily decomposed by hydrocracking over a long period of time. Moreover, when an organic nitrogen compound has a boiling point of 200 degrees C or less, since molecular size is also comparatively small, it is thought that it is not able to fully cover an acidic point, and it leaves easily from an acidic point.

According to the method of the present invention, the organic nitrogen compound is treated by contact with a hydrocracking catalyst before starting the hydrocracking operation. In the present invention, in contrast to the method described in the above-mentioned known document, the organic nitrogen compound defined in the present invention is brought into contact with the catalyst before the hydrocracking operation rather than during the hydrocracking operation. In this way, the specific organic nitrogen compound is contacted with the catalyst in advance before the hydrocracking operation to cover the acid point of the catalyst with the organic nitrogen compound, so that even a small amount of the organic nitrogen compound is effective for preventing catalyst deterioration over a long period of time. The amount of organic nitrogen absorbed in the catalyst can be maintained, for example, from 0.01% to 1% as the weight of nitrogen relative to the catalyst.

The method of the present invention may further comprise a step of sulfiding the catalyst for hydrocracking, and the treatment of contacting the organic nitrogen compound with the catalyst for hydrocracking is preferably performed simultaneously with the sulfiding treatment. Mixing tert-butylamine (bp: 44 ° C.) and diesel fuel dissolved in sulfided carbon sulfide (CS ₂ ), which has been conventionally used, produces a white precipitate, but an organic nitrogen compound having a boiling point of 200 ° C. or higher according to the present invention. For example, even if tributylamine (bp: 217 degreeC) is mixed with diesel, it does not produce white precipitate. Therefore, by performing the pretreatment using the organic nitrogen compound simultaneously with the sulfidation treatment, the process can be simplified and the time required for the entire process can be shortened.

According to a second aspect of the present invention, in the hydrocracking method of hydrocarbon oil derived from petroleum,

Contacting a petroleum fraction comprising an organic nitrogen compound to a catalyst for hydrocracking, having a 95% effluent temperature substantially lower than 50% effluent temperature of the crude oil consisting of hydrocarbon oil and higher than 200 ° C., and

Contacting the raw material oil and hydrogen to a hydrocracking catalyst contacted with the petroleum fraction to obtain a hydrocarbon oil having a boiling point lower than that of the raw oil.

Provided is a hydrocracking method comprising a.

Also in the hydrocracking method of this aspect, as in the first aspect, (i) relaxation of the initial deterioration rate of the hydrocracking catalyst, (ii) improvement of intermediate fraction yield, and (iii) improvement of activity after completion of the initial degradation Can be achieved. In the hydrocracking method of this aspect, the petroleum fraction lower than the 50% outlet temperature of the raw material oil and the 95% outlet temperature higher than 200 ° C is, for example, light oil and kerosene. The boiling point of light oil is 220 degreeC-380 degreeC, and the boiling point of kerosene is 140 degreeC-250 degreeC. Such petroleum fractions used in the present invention include organic nitrogen compounds such as aniline, pyridine, quinoline, indole, carbazole or derivatives thereof and the like. Since these organonitrogen compounds are contained in petroleum fraction having a 95% distillation temperature higher than 200 ° C, it is considered that the acid sites of the catalyst can be protected for a long time in the hydrocracking process. In order to carry out the method of this aspect, the hydrocracking catalyst may be treated by, for example, contacting with light oil or kerosene in advance. The light oil is a straight run gas oil obtained by atmospheric distillation of crude oil, a light oil obtained by desulfurization of coker gas oil, a vacuum gas oil through a pyrolysis device, mixtures thereof, hydrogenated tablets thereof Light oil obtained by the above can be used.

According to the third aspect of the present invention, a hydrocracking catalyst used in a hydrocracking method for obtaining a hydrocarbon oil having a boiling point lower than that of the crude oil by bringing crude oil derived from petroleum and hydrogen into a hydrocracking catalyst. To

A carrier composed of a porous refractory oxide;

Hydrogenated active metal component; And

Organonitrogen compounds with boiling points below 50% distillation temperatures of crude oil and above 200 ° C

Including,

The content of the organic nitrogen compound is 0.01 wt% or more by weight of nitrogen with respect to the catalyst for hydrocracking.

A catalyst for hydrocracking is provided.

Since the organic nitrogen compound having an excessively large molecular size must be removed, the hydrocracking catalyst preferably does not include a nitrogen compound having a boiling point exceeding 50% outlet temperature of the raw material.

The raw material oil which is a starting material of the hydrocracking process of the present invention is a raw material oil having a 10% outlet temperature of usually 200 ° C or higher, and preferably a raw oil having a 10% outlet temperature of 300 ° C or higher. The raw material oil is not particularly limited, but one derived from crude oil, coal liquefied oil, oil shell, oil sand, or the like, Fischer-Tropsch synthetic oil, or the like is preferably used. The hydrocracking method and catalyst of the present invention are particularly effective for crude oil hydrogenated to a nitrogen content of 100 ppm or less, especially 10 ppm or less, more preferably 2 ppm or less. Such hydrogenated crude oil corresponds to, for example, crude oil that has undergone hydrocracking in the first stage during two-stage hydrocracking.

1 to 5 show typical examples of the process flow of the hydrocracking system to which the hydrocracking method of the present invention can be applied. In the system shown in FIG. 1, there is only one stage of reactor, and in the system shown in FIG. 2, there are two stages of reactors. The systems shown in FIGS. 3 to 5 each have a circulation path from the distillation column to the reactor. By the system shown in FIG. 4, after the raw oil is hydrocracked in the first stage reactor 41, it is transferred to the distillation column 43 to recover the light oil and the remaining heavy oil is transferred to the second stage reactor 45. do. After hydrocracking is carried out in the second stage reactor 45, the oil is transferred back to the distillation column 43. In the system shown in FIG. 5, the first stage reactor, the second stage reactor and the distillation column are connected in this order, and heavy oil is circulated from the distillation column to the second stage reactor. In the systems shown in Figs. 4 and 5, in the reactor of the second stage, once the hydrogenation tablet is performed in the reactor of the first stage, it is very suitable for the application of the hydrocracking method of the present invention. Therefore, the hydrocracking catalyst of the present invention is very suitable as a catalyst used in the second stage reactor of the two or multiple stage hydrocracking systems shown in FIGS. 4 and 5, respectively.

However, the present invention can also be applied to the case of performing hydrocracking by the process flow as shown in Figs. 1 and 2 by using at least one hydrogenated fraction as a raw material.

Hydrocracking of the present invention is a process of obtaining oil equivalent to kerosene, light oil, etc., which is lighter than raw oil, and specifically, the boiling point range is 300 ° C. or lower, especially 125 ° C. to 300 ° C., in a yield of 50% or more. Catalyst and operating conditions are selected to obtain.

The catalyst used is formed by supporting a hydrogenated active metal component or the like on a carrier made of a porous refractory material. Examples of the carrier include alumina, boria-alumina, silica-alumina, silica-titania, silica-zirconia, silica-magnesia, silica-alumina-titania, silica-alumina-zirconia, and mixtures thereof, zeolites, etc. This is preferably used. Further, as the hydrogenated active metal component, Group 6 metals, Group 9 metals, and Group 10 metals of the periodic table are preferably used. Specifically, tungsten, molybdenum, nickel, cobalt, and the like can be used, and in particular, tungsten or molybdenum It is preferable to combine with nickel and cobalt. It is preferable to use 1-35 weight%, especially 5-30 weight% of these metal components as a total weight of metal with respect to a catalyst weight.

The organic nitrogen compound used in the present invention is an organic nitrogen compound having a boiling point above 200 ° C., which is lower than 50% effluent temperature of the raw material, especially (50% effluent temperature (° C.)) × (0.9), or 95%. A nitrogen compound containing petroleum fractions above 200 ° C. with an outflow temperature below the 50% outflow temperature of the crude oil, in particular below (50% outflow temperature (° C.)) × (0.9). Specific examples include organic nitrogen compounds such as amines, pyridine, quinoline, indole and carbazole. Further, derivatives of such organic nitrogen compounds or derivatives of other organic nitrogen compounds having boiling points above 200 ° C. such as aniline derivatives can be used.

The amount of the organic nitrogen compound contained in the hydrocracking catalyst of the present invention is 0.01% or more as the weight of nitrogen, particularly preferably 0.1% to 1%. The organic nitrogen compound used in the present invention has a boiling point range as described above and is in contact with the catalyst prior to the hydrocracking process, so that the amount of addition is very small as compared with the conventional nitrogen compound additives.

The organic nitrogen compound may be added at the time of preparing the catalyst, but the catalyst may contain the nitrogen compound by contacting the catalyst with the nitrogen compound after the catalyst is charged to the reactor. When the organic nitrogen compound is brought into contact with the catalyst after being charged to the reactor, it is efficient as a process to contact the nitrogen compound before the hydrocracking reaction, for example, during presulfurization. In addition, the organic nitrogen compound may be brought into contact with the catalyst prior to the hydrocracking reaction, and then the nitrogen compound may be added to the reactor during the hydrocracking reaction to make contact with the catalyst. In this case, the nitrogen compound may be blended with the raw material oil which is a raw material for the decomposition reaction, or may be mixed with a gas such as hydrogen introduced into the reactor. The nitrogen compound added during the hydrocracking reaction functions as a catalyst for inhibiting deterioration of the catalyst, and may be ammonia or other nitrogen compounds in addition to the organic nitrogen compounds described above.

The organic nitrogen compound used in the present invention may be used as the compound single compound, but it is more simple to use the organic nitrogen compound contained in the petroleum fraction. Specifically, commercially available kerosene, diesel oil and the like can be used, and a hydrogenated additive having a nitrogen content of 2 to 200 ppm, preferably 2 to 100 ppm, particularly 10 to 100 ppm is preferably used. The sulfiding agent is brought into contact with a solution dissolved in a solvent such as kerosene, diesel, or the like to bring the catalyst into sulfidation, whereby the organic nitrogen compound can be included in the catalyst as a result of the sulfidation treatment. Carbon sulfide, dimethyl sulfide, dimethyl disulfide, etc. can be used as a sulfiding agent.

EXAMPLE

In the case where kerosene or diesel oil is produced by a two-stage hydrocracking method using a system as shown in FIG. 4 using reduced pressure diesel oil, the catalyst charged in the second stage reactor 45 is added to the organic nitrogen compound. The embodiment processed by contact is described below.

Example 1

The raw material oil supplied to the 1st stage reactor 41 of the two stage hydrocracking system shown in FIG. 4 is petroleum fraction whose boiling range is 300 degreeC-540 degreeC, and nitrogen concentration is 800 ppm. The oil produced from the first stage reactor 41 is distilled in the distillation column 43, and the effluent from the bottom of the distillation column 43 becomes the raw material oil (recycle oil) of the second stage reactor 45. The product oil of the second stage reactor 45 and the product oil of the first stage reactor 41 are mixed and supplied to the distillation column 43. The raw material oil of this second stage reactor 45 has a boiling point range of 290 ° C to 540 ° C and a nitrogen concentration of 1 ppm. As a catalyst, a catalyst for hydrocracking containing nickel and tungsten metal components in a silica-alumina support in both the first stage and the second stage reactors was used.

Before carrying out hydrocracking, the oil in which 1 wt% of carbon disulfide was added as a sulfiding agent to diesel oil (boiling point range 250 ° C. to 360 ° C.) is passed through the second stage reactor 45 to pass through the second stage reactor 45. The catalyst was presulfurized. The sulfur concentration in diesel was 400 ppm and the nitrogen concentration was 50 ppm. It was found that 17 ppm of acidic nitrogen compounds, which are indole and carbazole derivatives, and 16 ppm of basic nitrogen compounds, which are amines, aniline, pyridine, and quinoline derivatives.

The time the diesel oil passes through the reactor during the preliminary sulfidation was adjusted such that the nitrogen concentration adsorbed to the catalyst in the second stage reactor 45 was 0.4% (nitrogen weight / filled catalyst (untreated fresh catalyst) weight).

After completion of the preliminary sulfidation, the operation of the system of FIG. 4 was switched to a two stage hydrocracking operation to initiate hydrocracking. Hydrocracking operation was continued for 620 hours. Initial degradation rate was found to be 0.5 ° C./month or less. After completion of the initial deterioration, it was necessary to adjust the reaction temperature of the second stage reactor 45 to 377 ° C. in order to maintain a conversion of oil of 290 ° C. or more at 95 volume%. The yield of middle oil (130 degreeC-290 degreeC) was 66% (medium oil weight / raw material oil weight).

Example 2

Petroleum fraction having a nitrogen concentration of 1 ppm and a boiling point range of 290 ° C to 540 ° C was used as a raw material, and hydrocracking without recirculation was performed using a system equipped with a one-stage reactor as shown in FIG. As a catalyst, a catalyst for hydrocracking containing nickel and tungsten metal components in a silica-alumina support was used.

Prior to hydrocracking, presulfurization of the catalyst was carried out by passing an oil containing 1% by weight of carbon disulfide as a sulfiding agent through diesel oil (boiling range 250 ° C to 360 ° C). The sulfur concentration in the diesel oil was 400 ppm and the nitrogen concentration was 50 ppm. During preliminary sulfiding, the time for which diesel oil passes through the reactor is adjusted so that the concentration of nitrogen adsorbed to the catalyst in the reactor becomes 0.4% (weight of nitrogen / catalyst after passing through).

After completion of the preliminary sulfidation, the hydrolysis was initiated with the reaction temperature constant at 380 ° C. As a result, the decomposition rate of the oil at 290 ° C or higher was 56%, and the yield of the intermediate fraction (130 ° C to 290 ° C) was stable at 38%.

Example 3

As a catalyst in the second stage reactor, the catalyst was presulfurized under the same conditions as in Example 1 except that 1% zeolite was added to the support, and hydrocracking was carried out. The reaction temperature of the second stage reactor where the decomposition rate of the oil content of 290 ° C or more became 95% by volume was 377 ° C. The yield of middle fraction (130 degreeC-290 degreeC) was 64%.

Example 4

In Example 3, 0.3 ppm of tert-butylamine (catalyst deterioration inhibitor) was incorporated as a nitrogen concentration into the feedstock oil to the second stage reactor during the hydrocracking operation. The reaction temperature of the second stage reactor where the decomposition rate of the oil content of 290 ° C or more became 95% by volume was 379 ° C (2 ° C higher than Example 1). The yield of middle fraction (130 degreeC-290 degreeC) was 67%.

Example 5

Hydrocracking was carried out in the same manner as in Example 4 except that 10 ppm of tert-butylamine (catalyst deterioration inhibitor) was mixed in the raw material oil to the second stage reactor as a nitrogen concentration. The temperature of the second stage reactor at which the decomposition rate of the oil content of 290 ° C or more became 95% by volume was 390 ° C. The yield of middle fraction (130 degreeC-290 degreeC) was 67%.

Comparative Example 1

Hydrocracking was carried out under the same conditions as in Example 1 except that the diesel oil used for preliminary sulfidation was changed to diesel gas having a nitrogen concentration of 1 ppm. The nitrogen concentration adsorbed to the catalyst in the second stage reactor 45 during the preliminary sulfiding was 0.003% (nitrogen weight / weight of catalyst (new catalyst) after adsorption treatment).

As a result of starting hydrocracking in the same manner as in Example 1, the initial deterioration rate was 2 ° C / day. In order to maintain the decomposition rate of the oil content of 290 degreeC or more after being 95 volume% after completion | finish of initial stage deterioration, it was necessary to maintain the temperature of the 2nd stage reactor 45 at 384 degreeC. The yield of middle oil was 65.4% (medium oil weight / raw oil weight). Compared with Example 1, since the amount of nitrogen poisoning of the catalyst is small, it can be seen that the initial degradation rate is high, the activity after completion of the initial degradation is low, and the middle oil yield is low.

As described above, according to the present invention, the hydrocracking catalyst is an organic nitrogen compound having a boiling point lower than 50% of the crude oil and having a boiling point of 200 ° C. or higher, or a petroleum oil having a 95% outlet temperature lower than the 50% of the crude oil. By poisoning with the nitrogen compound contained in the catalyst, the initial deterioration rate of the hydrocracking catalyst was alleviated, the activity after the end of the initial deterioration was improved, and the intermediate fraction yield was improved. As a result, hydrocracking can be operated for a long time with good efficiency.

Claims (14)

In the hydrocracking method of hydrocarbon oil, Contacting a catalyst for hydrocracking with an organic nitrogen compound in advance; And Contacting hydrogen with crude oil consisting essentially of hydrocarbon oil to a hydrocracking catalyst contacted with the organic nitrogen compound to obtain hydrocarbon oil having a lower boiling point than crude oil; Including, And the organic nitrogen compound is an organic nitrogen compound having a boiling point lower than 50% distillation temperature of the raw material oil and higher than 200 ° C. In the hydrocracking method of hydrocarbon oil derived from petroleum, Contacting a petroleum fraction containing an organic nitrogen compound to a catalyst for hydrocracking having a 95% effluent temperature substantially lower than 50% effluent temperature of the crude oil consisting of hydrocarbon oil and higher than 200 ° C .; And Contacting raw material oil and hydrogen to a hydrocracking catalyst contacted with the petroleum fraction to obtain a hydrocarbon oil having a boiling point lower than that of the crude oil Hydrocracking method comprising a. The method of claim 1, Further comprising the step of sulfiding the hydrocracking catalyst, the hydrocracking step of simultaneously contacting the organic nitrogen compound with a hydrocracking catalyst and a sulfiding step of the hydrocracking catalyst. Way. The method of claim 2, A hydrocracking method further comprises the step of sulfiding the hydrocracking catalyst, wherein the step of contacting the petroleum fraction with the hydrocracking catalyst and the sulfiding step of the hydrocracking catalyst. The method of claim 2, The hydrocracking method in which the said petroleum fraction contains an organic nitrogen compound of 2 ppm or more as a weight of nitrogen. The method according to claim 1 or 3, A hydrocracking method comprising 0.01% to 1% of an organic nitrogen compound as the weight of nitrogen per unit catalyst weight in the hydrocracking catalyst by contacting the organic nitrogen compound with a hydrocracking catalyst. The method according to any one of claims 2, 4 and 5, A hydrocracking method comprising 0.01% to 1% of an organic nitrogen compound as the weight of nitrogen per unit catalyst weight in the hydrocracking catalyst by bringing the petroleum fraction into contact with the hydrocracking catalyst. The method according to claim 1 or 2, A hydrocracking method wherein a catalyst deterioration inhibitor is added when the raw material oil and hydrogen are brought into contact with a catalyst for hydrocracking. The method of claim 8, Hydrocracking method wherein the catalyst deterioration inhibitor is a nitrogen compound. The method of claim 9, The hydrocracking method of which the addition amount of the said inhibitor is 5 ppm or less as a weight ratio of nitrogen with respect to raw material oil. The method according to any one of claims 2, 4 and 5, Hydrocracking method wherein the petroleum fraction is diesel. In the hydrocracking catalyst used in the hydrocracking method of obtaining a hydrocarbon oil having a boiling point lower than that of crude oil by contacting raw oil derived from petroleum and hydrogen with a catalyst for hydrocracking, A carrier composed of a porous refractory oxide; Hydrogenated active metal component; And Organic nitrogen compounds having a boiling point below 50% distillation temperature of crude oil and higher than 200 ℃ Including, A catalyst for hydrocracking, wherein the content of the organic nitrogen compound is 0.01 wt% or more by weight of nitrogen relative to the catalyst for hydrocracking. The method of claim 12, A catalyst for hydrocracking, wherein the organic compound is an organic compound contained in diesel or kerosene. The method according to claim 12 or 13, A catalyst for hydrocracking, prepared by contacting a solution of a sulfiding agent dissolved in light oil or kerosene with a catalyst having the carrier and the hydrogenated active metal component.